feat: add Docker support for cross-platform easy setup

Implements comprehensive Docker support to eliminate Python version and dependency concerns.
Users can now run the MCP server in a container with automatic path translation between
host and container filesystems.

Key features:
- Dockerfile with multi-architecture support (amd64/arm64)
- Automatic path translation using WORKSPACE_ROOT environment variable
- Setup scripts for all platforms (Bash, CMD, PowerShell)
- GitHub Actions workflow for automated Docker Hub publishing
- Secure non-root container execution
- Read-only volume mounts by default

The setup process is now simplified to:
1. Run setup-docker-env script to generate .env and Claude config
2. Build the Docker image
3. Copy generated config to Claude Desktop

No Python installation or virtual environment management required.

Fixes #3

Co-Authored-By: Claude <noreply@anthropic.com>

.env.example

@@ -0,0 +1,15 @@
+# Example .env file for Gemini MCP Server Docker setup
+# Copy this to .env and update with your actual values
+
+# Your Gemini API key (required)
+# Get one from: https://makersuite.google.com/app/apikey
+GEMINI_API_KEY=your-gemini-api-key-here
+
+# The absolute path to your project directory on the host machine
+# This will be mounted to /workspace in the container
+# Example: /Users/username/my-project (macOS/Linux)
+# Example: C:\Users\username\my-project (Windows)
+WORKSPACE_ROOT=/path/to/your/project
+
+# Optional: Logging level (DEBUG, INFO, WARNING, ERROR)
+# LOG_LEVEL=INFO